So this is a long story but I'll try to keep it short!

I 29m met a girl 20f in a local pub almost a year ago. She came up to me and we spoke for a bit until she took my phone and put in her number. Now at first I was a bit hesitant because of the age gap! However we got on well so I thought why not!

We started speaking for a couple of days over text and phone calls. She then told me she has a boyfriend but isn't really happy in the relationship. She would go a couple of days without replying because she didn't want him to see her speaking to me. We never went out and after a few weeks I gave up because I wasn't into ruining a relationship.

Fast forward 6 months, we ran into each other again at a local bar due to a mutual friend. Instant fireworks once again. This time she tells me she's broke up with her boyfriend so I thought ok well I'll see where it goes. For the next couple of months we spoke all the time, went on a few dates and she'd stay over at my apartment. I told her that I had feelings for her and I wanted a relationship. This is when I find out that she was still talking to her ex and still seeing him.

For about another month I carried on speaking to her and seeing her because I thought she would possibly change her mind and went to be with me. Yes pretty delusional but when you start to fall for someone you don't want to let go! After a while I had to block her and completely cut her out of my life because I couldn't continue wanting to be with her knowing that it wouldn't happen, she made that quite clear!

Fast forward again to about a month ago, this is after around 4 months of not speaking and 1 other situationship later! We run into each other again! She started being very affectionate towards me and making the effort to come up to me and talk etc.. we ended up kissing at the end of the night and I gave her a lift home. The next night she messaged me and asked me to go see her, we ended up sat in my car just talking for 6 hours. She told me that she's still seeing her ex and stays at his twice a week etc..

Now this time for some reason I don't feel like I want a relationship with her but I will happily just have. Something casual and not ready care. Oh how wrong I was with that feeling!

I've not been trying to put in any effort and sort of let her come to me rather than me chasing her this time. Now this time it feels so different, it's like she wants me and tells me how compatible we are and she's never felt like she can be so open and relaxed around someone.

Now my question is, how do I play this out? She seems to be more interested this time around and feels like she possibly will want things to go further. However with her ex being involved it's like she doesn't want to completely move on for some reason.

I won't give her an ultimatum or force her to make a choice because that's one way to ruin everything! I don't want to tell her that I have feelings for her again and I'm completely smitten! But I don't want to get too invested and it go for a while for me to completely fall in love with her just to have my heart broken!

Has anyone been in a similar situation or have any advice on where to go from here?

I have been told, just walk away, block her etc.. but I want her because it's just so natural when we're together and everything just feels right!

Sorry about the long post, it youve read it all I appreciate you dealing with my waffling!

Tldr: same girl has come into my life 3 times. She's still involved with her ex. Tells me that she wants me but I can't tell her to make a choice between me and her ex without pushing her away. I also can't walk away from her because every fibre of my being is telling me she is the one.